The question comes up all the time — which has the most caffeine, light roast or dark roast?
Almost everyone seems to know the answer. Right?
Except pretty much every one is wrong because it turns out if you are looking for high caffeine content, light roast vs dark roast is the wrong question.
So here’s the skinny on coffee roasting and caffeine.
On the average, a coffee bean loses 90 percent of its water content during the roasting process. The longer a coffee bean is roasted (meaning the darker the roast), the more water it loses. But even with that, the water loss between light roast and dark roast is fairly minimal. And water loss really does not affect caffeine content much.
At least outside of the fine measurements of a scientific laboratory, roasting time does not affect caffeine content in a coffee bean much at all. Roasting does however shrink the coffee bean (due to water loss). And the longer a bean is roasted, the more it shrinks.
Because of water loss, there is an average of a 9-bean difference per pound of coffee between light roast & dark roast.
So, at least technically, you get more coffee for your money if you buy light roast. By 9 whole beans a pound.
But let’s get back more specifically to caffeine content. If we are going to be clinically precise, how you measure your coffee makes a difference in which roast has a higher caffeine content.
IF YOU MEASURE BY THE SCOOP, which means you are measuring your coffee by volume, you get slightly more caffeine in a cup of light roast coffee because you are putting an extra bean in a your coffee 9 mornings out of the time it takes you to drink a pound of coffee.
IF YOU MEASURE BY WEIGHT, you get slightly more caffeine in a cup of dark roast coffee because the shrunken bean is lighter than the bean with more water in it. So you use more coffee when you measure dark roast by weight.
But the difference between light roast and dark roast caffeine levels is negligible either way.
It turns out that really and truly, the only difference between light roast, medium roast, and dark roast coffee is taste. It’s not caffeine. And although there may be a slight difference in lab measurements, it is way too tiny to be noticeable by humans who drink it.
The taste of light roast is decidedly brighter and crisper, some say more acidic although most who prefer light roast don’t describe it as acidic. They say it is sweeter than dark roast.
The taste of dark roast is darker and more somber. Afficionados say it is smoother than light roast. Those who prefer light roasts say dark roast is more bitter.
Medium roast splits the baby by throwing it into the spectrum between.
But if caffeine, rather than taste, is the driver in coffee choice — asking which roast is the wrong question.
The right question is which species of coffee.
The two main commercial coffee species are Arabica and Robusta.
Arabica is quite a bit more expensive than Robusta. And it has anywhere from 65 percent to 90 percent less caffeine than Robusta. It also tastes a lot better than Robusta to most people’s palates. The taste, of course, is the reason Arabica is more expensive.
Robusta is way cheaper than Arabica. And conversely Robusta has 65 percent to 90 percent more caffeine than Arabica. It just doesn’t taste very good — which is why it is cheap.
IT TURNS OUT, CAFFEINE DOESN’T REALLY TASTE ALL THAT GOOD in high levels.
So if you drink coffee primarily for the caffeine, you are in luck. You just may be buying the wrong coffee. Simply switch your next coffee purchase to the much cheaper Robusta and you will get the kick-per-cup you are seeking.
If the beans are Arabica beans, then either roast has pretty much the same caffeine level. Roast is a matter of taste, not of caffeine.
Personally, I am all for drinking two cups of the one that tastes better.
But to each her own!